minimum drain pipe size for a lav

[poky1234]

Hello, Can someone tell me if an 1 1/4 pipe can be used to drain a lav? The drain pipe would run 4 to 5 feet ,then connect into the vertical 3 inch main waste stack. Also , because of the short distance,would it still require its own vent?

Thanks

[cacher_chick]

In the U.S., the trap and trap arm of a lav is commonly 1-1/4", but the drain is run in 1-1/2".

From the International Plumbing Code (IPC)

[Terry]

The lav should have a vent before it enters any "waste" stack.

A lav can wet vent a shower, tub or toilet, but you can not run down waste on top of it in that manner.

[mikeplummer]

it can be 1-1/4" drain and can be stack vented if there is no discharge upstream of where it connects to the 3" main. If there is discharge from above that connection then it does require tis own separate vent

[poky1234]

it can be 1-1/4" drain and can be stack vented if there is no discharge upstream of where it connects to the 3" main. If there is discharge from above that connection then it does require tis own separate vent

Thanks for the replies guys. Mikeplumber, that is exactly what we are doing. I just needed to know if 1 1/4 is ok. This is for a custom floating boathouse that has very tight quarters and is a little unconventional. I have another question but I'll post it with a pic and drawing.